Automated unwanted telephone calls have become problematic for many users and it is known to use telephone answering machines or systems to block calls which are from unidentified numbers, which are from numbers held in a blacklist (or alternatively are not present on a whitelist), or which are from numbers of a particular category (for example international calls). An example of such a system is disclosed in GB-B-2 425 913. However, it would be preferable if such calls could be blocked within the operator's networks, such that the customer does not need to take significant action or acquire specific equipment in order to not be disturbed by the automated unwanted calls.
Automated unwanted calls are typically initiated by a computer dialler and, when answered, a pre-recorded message is played back to the called party. If the called party does not respond at the end of the pre-recorded message, for example by pressing a button in response to an option set out in the pre-recorded message, then the call will automatically terminate. It will be understood that a bank of computer diallers can generate a significant number of calls within a limited period of time.